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The latest effort to come up with a male birth control pill has found a formulation that appears to be safe, researchers at the University of Washington said.

NBC News reported that Stephanie Page and her team are testing dimethandrolone undecanoate, a tweaked version of previous failed efforts to develop a male pill. Possibly the best hope yet for a non-permanent male contraceptive, it's being developed with funding from the National Institutes of Health.

But the experimental pill has at least one of the same problems that plague female birth control pills: it caused the men to gain weight. And after just a few weeks of testing, it’s also not yet clear how well it works.

Even though the researchers said they were “very excited” by the results, they haven’t been testing it long enough to show whether it decreases sperm production, and they haven’t shown whether it stops couples from conceiving.

Total Lunar Eclipse Comes with Supermoon Bonus

On Sunday night, the moon, Earth and sun lined up to create an eclipse, which was visible throughout North and South America, where skies were clear. It was also the year's first supermoon, when a full moon appears a little bigger and brighter. (This video does not have audio)